Reduction of finely divided metal compounds



N0V- 16 1943 R. 1 PATTERSON REDUCTION OF FINELY DIVIDED METAL. COMPOUNDS Filed Nov. s, 1941 5 sheets-sheet 1 N0V 16 1943' R. L. PATTERSON 2,334,434 REDUCTION OF FINELY DIVIDED METAL COMPOUNDS Filed NOV. 3, 1941 5 Sheets-Sheet 2 Nov. 16, 13943.

REDUCTION OF FINELY DIVIDED METAL COMPOUNDS Filed Nov. 5, 1941 5 Sheets-Sheet 3 IN ENTOR PQZZerJa/a ATTORNEYS aJ/mowd w i ll V g C u f l IJ f l/ f n n n 4 n, f.. f., L A A fm /f C 1 Patented Nov. 16,1943

fnlmUc'rroN or FINELY DIVIDED METAL CORIPOUNDS Raymond L. Patterson, New York, N. Y., assigner to Powder Metals and Alloys', Inc., NewYork, 1 1 N.y Y., a corporation o! Delaware -pplication November 3, 1941, Serial No. 417,607

solid material from the upper end of the hearth.V

ZCIaims.

This'inventionis' concerned with furnace treatment .of ,finely divided material in the solid state with various gaseous-treating agents. The invention is particularly adapted to the reduction of finely divided metal oxides and the like with 5 hydrogen gas, but may be employed in the treatvmeant of many finely divided solids with a variety of gaseous treating agents.

In the furnace treatment of many finely divided metal oxides and the like with hydrogen, the reaction products are finely divided metal and water vapor. If the water vapor is permitted to remain in contact with the freshly formed metal powder, it tends to react therewith, so that the reaction is reversed and the freshly formed metal powder is oxidized, at least on the surface. This tendency has caused difficulty in many heretofore customary processes for the manufacture of metal powder by reduction of oxides.

As the result of my investigations, I have developed an improvement that is applicable to the above-described and analogous processes in which a first finely divided material is ltreated with a.

gaseous reagentmto produce a second finely divided solid material and a gaseous reaction product that is heavier than the gaseous reagent. The improvement involves bringing the gaseous reagent into contact with the rst solid material while the latter is travelling upward through a reaction zone, withdrawing the resulting second material substantially continuously from an upper portion of the zone and withdrawing the gaseous reaction product substantially continuously from a lower portion of the zone. Preferably the solid material undergoing treatment In my preferred furnace structure, hydrogen or other gaseous reducing agent is introduced at the upper end of an inclined muille or trough, finely divided metal oxides or other material to be reduced being introduced at the other end of the muille. The finely divided metal oxide or the like is caused to travel upwardly in the trough countercurrent to the; hydrogen gas. The resulting water vapor is removed from the lower end of the trough while the resulting metallic particles travels upwardly on an incline, its motion being a pulsating one, with the gaseous reagent and the material passing in countercurrent. As indicated above, the process is particularly suitable for the treatment of a metal compound (say iron oxide) to form a metal (iron), the gaseous reagent being hydrogen with water as a gaseous reaction product, but the process is applicable to other materials.

The foregoing process preferably is conducted in an apparatus of my invention comprising a furnace chamber, an inclined hearth (preferably enclosed in a. muiiie) passing through the furnace or heating chamber, means for feeding nely divided solids onto the lower end of the hearth, means for bringing a gaseous treating agent into contact with the solids on the hearth, means for imparting oscillations to the hearth to cause the solid material to move upwardly thereon, and means for discharging the treated are removed from the upper end. In this way, the water vapor is kept out of contact with the metal powder and the danger of reaction reversal is obviated. The muiiie or trough in which the gas and metal compound are reacted passes through the heating chamber and the finely divided Solids are caused to move upwardly in the Inutile by imparting oscillations thereto. The muliie is movably mounted and is oscillated in a longitudinal direction by means of a cam mechanism, vibrator, or the like.

These and other features of my invention. will be more thoroughly understood in the light of the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a longitudinal elevation, partly in section, through one form of the furnace for practicing my invention;

Fig. 2 is a plan, partly in section, of the apparatus of Fig. 1;

Fig. 3 illustrates a modified form of the furnac'e structure of Figs. 1 and 2 provided with a muflie having a porous hearth;

Fig. 4 is a section taken through the muiile of the apparatus of Fig. 3 along the line 4 4;

Figs. 5 and 6 are diagrammatic longitudinal elevations illustrating further modifications of the apparatus of Figs. 1 and 2;

Fig. 7 is a plan view showing a furnace structure for practising my invention including a plurality of parallel muiiles in which metal compounds to be reduced and the reducing gasmay be moved in countercurrent with each other;

Fig. 8 is an elevation, partly in section, of the ing means, for example, a plurality of burners I2, I2A, I2B, et seq. to I2H are provided within the heating chamber. Gaseous products of combustion from the burners may be withdrawn from the heating chamber through a plurality of flues The heating chamber is provided with a longitudinally sloping bottom I4 over which is sus- I pended a sloping trough or muilie I5 of heat conductive material. The trough slopes upwardly from right to left as shown in Fig. 1. The mate- In the furnace, the hot hydrogen ows in counf tercurrent to the finely divided metallic compound to be reduced. The oscillations imparted to the muflle cause the'flnely divided iron oxide to travel upward along the bottom of the muile, which is sloped at a slight angle, say 5 from the horizontal. As the hydrogen gas reacts with the iron oxide, 4water vapor is formed. This water vapor is heavier than the hydrogen so that it tends to sink in the trough and is withdrawn through an outlet 22 at the lower end of the trough. The finely divided iron formed by reduction passes to the upper end of the trough and gravity toward the lower end of the hearth and is withdrawn through an outlet conduit 29. The metallic iron resulting from reaction of the iron oxide and the hydrogen passes to the upper end of the hearth and is withdrawn throimh a valve into a conventional cooler 3 I.

In the apparatus of Fig. 3, the flow of hydrogen and iron oxide is generally countercurrent, although not completelyr so. In anyV event, the fact' that one end of the muflle is lower than the other end prevents the freshly reduced iron from coming in contact with the other product of reaction, i. e. the water vapor.

As indicated above, Fig. 4 is a transverse section taken through the mule and shows the porous hearth 25, which may be of a suitable refractory, located within the mufile and overlying the vapor space 26 into which the reducing gas is introduced.

The apparatus of Fig. 5 is, in general, similar to that of Figs. 1v and 2 (like elements being designated by the same characters as in Figs. 1 and 2). It differs from the apparatus of Figa-1 and 2, however, in that the hydrogen is admitted thence into a hopper 23` from which it may be withdrawn through a valve 24 into a conventional cooler, not shown. The freshly formed iron pow,- der is pyrophoric and should be cooled to about room temperature in the absence of -any oxidizing influences including water vapor.

y It will be observed that in the apparatus of Figs. l and 2, the water vapor formed tends to `ilow by gravity into the lower portion of the trough and thus is prevented vfrom coming into contact with the completely reduced metal powder.

The mule may be made of any convenient material. For example, it may be made of heat resisting steel, provided that the temperature of treatment does not rise too high, say, in excess of aboutlOGO" C.

The apparatus of Fig. 5 is,`in general, similar to that of Figs. 1 and 2, like elements being des'- ignated by like numbers. However, in the apparatus of Fig. 3 the burners I2 are positioned both above and below the mufe in the heating chamber and the mule is provided with an interior porous hearth 25. Hydrogen gas or other gaseous reducing agent to be reacted with the finely divided metallic compound (say iron oxide) in the furnace is introduced into'a vapor space 26 underneath the porous hearth under pressure.

Thus, hydrogen may be introduced into the vapor space underlying the porous hearth in the mufe through conduits 21, 28 at both ends of the furnace. As in the case of the furnace shown in Figs. 1 and 3, the mufe slopes upwardly to the left. Finely divided solids are caused to travel upwardly along the porous hearth by oscillation of the muffle. The hydrogen gas is brought into intiinto the muflle' at a plurality of points along its length. Thus, the hydrogen gas is admitted into the mufile through a, manifold 32 provided with a plurality of outlets 32A, 32B, 32C, 32D connected to the, top of the muflie. A large portion of the manifold is actually within the heating chamber of the furnace structure so that the hydrogen or other reducing gas is pre-heated prior to its contact with the metallic compound to be reduced.

The apparatus of Fig. 6 differs from that of Figs. 1 and 5, inclusive, in that vibration or oscillation is imparted to the muiile by means of a vibrator 33 `which bears against the outside of the lower end of the muie. The upper end of the muiile is supported on aspring 34 which in turn is supported in a jack 35 .so that the slope of the muflle can be adjusted slightly. The muille is held in position in theI heating chamber by means of a heavyanchor 36 attached 'to its lower end by a hinge or pivot. As in all "of the previous cases hydrogen is introduced into the upper end of the mule while the solid material is introduced into the lower end of the mule. These two materials pass in countercurrent with each other through the mulile so that water vapor is withdrawn from an outlet conduit at the lower end of the conduit while freshly reduced metal powder is withdrawn from the upper end of the mufIle.

To consider the apparatus of Figs. 7 and 8, it will be observed that it is in general like 'that of Figs. l and 2 except that it has a plurality of muies IBA, IBB, I5C, I5D, IEE, I5F, IBG connected in parallel within a single heating chamber. These mules may be of any convenient cross-section, for example, they may be in the form of cylindrical tubes. The solid material to be reduced to metal powder or the like is introduced into each muille from an individual hopper connected with its lower end. The metal compound'so introduced passes in countercurrent with the reducing gas (say hydrogen) introduced into the upper end of each mule through inlets which in turn are connected through valves to a hydrogen manifold. All of the muffles are oscillated by a single prime mover such as a motor-driven sha-ft 40, provided with a plurality of eccentric cams, 4IA, MB, MC, MD, ME, MF, -4IG which are connected to the respective muffles by a plurality of rods 42A et seq.

i i l i l n of the muilie so that re-oxidation of the iron to IZG. The apparatus is so constructed that each muiiie may be thrown out of service `without interfering with the operation of the other muilies. For example, one muille may be thrown out of service by disconnecting or loosening its cam and interrupting the feed of hydrogen gas and iron oxide at its two ends. When the operation is thus interrupted the muilie may be withdrawn completely from the heating chamber for cleaning or repair.

Fig. 9 illustrates a modification of the 'apparatus for practising my invention in which the mui'tie is provided with a plurality of loosely mounted scrapers in the form of interior chains 50A, 50B, 50C, 50D, 50E, EOF, 50G. These chains are hung within the muiiie in a longitudinal series and drag' along the floor of the mufile.

hearth or muille bottom and advanced upward to discharge at the upper end. The movement of the solid material up the hearth is accomplished by pulsating or, oscillating the material.'

I prefer to employ a hearth that is enclosed in section .and may have a hearth that is fiat or in th'eform of a convex or concave trough. If there is no hazard of explosion the hearth is not necessarily enclosed (i. e. it may be the bottom .of an open trough) but this is a preferred structure and it is almost essential when dealing with such re'active gases as hydrogen.

To consider a specific example of the operation of the apparatus of my invention, say, the apparatus of Figa-1 and 2, iron oxide is introduced continuously into the lower end of the inclined muiile while hydrogen gas is introduced substantially continuously atl the opposite end of the mufile. The iron oxide Aadvancesup the incline and is reduced by the hydrogen to metallic iron powder, the temperature within the mufiie being maintained adequately high, say, in the neighborhood of 800 C. by means of the burners or other heating devices in the heating chamber.

powder is prevented.

The apparatus is useful with a variety of finely-divided reducible metal compounds and with a variety of gaseous agents. It is particularly applicable when the gaseous reaction product is considerably heavier than the original gas, an example being an operation in which hydrogen is converted into Water vapor.

The operation of the apparatus for practising my invention may be continuous, particularly when a plurality of muiiies in parallel is employed. Thus, the apparatus of Fig. 7 may be operated for indenite periods. Should a muiile require cleaning, it may be withdrawn from service and cleaned without interrupting the operation of the other muilles in the structure. v The apparatus has a high capacity in terms of its volume and brings about a thorough reduction of'a variety-of metallic compounds, probably because'the oscillations imparted to the muille tend to roll the Vparticles over so that no portion is permitted to pass through the furnace except after thorough contact with the hydrogen.

The modification illustrated in Fig. 9 may be employed advantageously whenever the solid material undergoing treatment is of such a nature that it tends to ball-up or stick to the sides or bottom of the muilie. Thus the apparatus is provided with loosely mounted scraper members, in this instance chains. The latter are a very effective mechanism for breaking up agglomerations of oxides and metal powders, although of course the chains do interfere togsame degree with the passage of the material upwardly along the hearth.

I claim:

1. In a process involving the treatment of e.

finely divided metal compounawuh s gaseous reducing agent to produce a powder of the metal and a gaseous reaction product that is heavier than the reducing agent, the improvement which comprises bringing the reducing agent into countercurrent contact with the nely divided Vmetal compound while the latter'v is moved upward along an incline by pulsations through a reaction zone, withdrawing the resulting metal powder substantially continuously from an upper portion of said zone, and withdrawing the gaseous reaction product substantially continuously from a lower portion of said zone.

The metalliciron resulting from reaction of the iron oxide and the hydrogen is discharged in the nely divided state at the top of the incline. The Water vapor resulting from the reaction is heavier than hydrogen and tends to sink into the lower end of the inclined tube or muiile, at which point it is removed. In this way, a zone of dry hydrogen is maintained at the upper end 2. In a. processvinvolving the treatment of a nely divided iron oxide with hydrogen to produce iron powder and Water vapor. the improve- CERTIFICATE `oF CONNECTION. Patent No. 2,55LIJI51I. v November 16, 19LI5.

RAYMOND L, PATTERSON.

It is hereby Certified vthat errorv appears in the printed specification ofthe above numberedpatent requiring correction as follows: Page 2, first column, line 55, for'` "5'" :resid- "5"; page 5, second column, line lffor "same" read -eome; andlthai: the said Letters Patent should be yreed with this` correction therein that the sem-e may onform to the record of the case l vin the Patent Office.

Signed and sealed this )4th lv:my of January, A.` D. 19.1414;

v l Henry van Andale,

(Seal) Acting Commissione; of Patents. 

